There is a need for rapid, sensitive and specific tests for detecting the presence of various chemical substances in the environment and in biological systems. For example, in warfare, the detection of chemical warfare agents, such as nerve gases, are of critical importance in order to permit personnel to protect themselves against the same. It would be helpful, therefore, if military personnel could carry with them devices which would almost immediately detect trace amounts of chemical warfare substances in the air. Likewise, simple test kits which would immediately and specifically detect the presence of substances in biological samples, such as blood samples, would permit more immediate and precise treatment of various pathogenic conditions.
The present invention utilizes lipid-protein membranes which mimic biological membranes as a means of chemical substance detection. Biomembranes in nature organize living matter by separating cells and cell components from their environment. They consist mostly of lipids and proteins in sheets only a few molecules thick. The lipids, with both water-repelling (hydrophobic) and water-attracting (hydrophilic) regions, form fluid bilayers in water that are selective barriers to polar molecules. Proteins in nature serve distinct functions in membranes as enzymes, receptors, pumps, energy transmitters, or as gates or channels to allow ions and molecules to pass through the membranes. Biomembranes are extremely sensitive to surface conditions, and performance of the membranes is closely related to surface conditions.
Lipid and lipid-protein membranes which mimic biological membranes have been investigated for practical utility. For example, mycelles in which an aqueous solution is encapsulated in an artificial membrane have been used as carriers of drugs, Fendler, J. C&EN Jan. 2, 1984 pp. 25-38, or as vesicles for hemoglobin as an artificial blood substitute.
As a means to investigate the fluid transport characteristics and other properties of lipid-protein membranes, artificial membranes known as black lipid membranes (BLM's) have been prepared across small
orifices, Fendler, J., Membrane Mimetic Chemistry, John Wiley & Sons, New York 1982. BLM's have had relatively little practical importance because (1) they are notoriously difficult to prepare and (2) they seldom last longer than several hours.
It would be desirable to have stable lipid-protein membranes that would permit their surface sensitivity to be utilized, for example, for the detection of chemical substances.